The Seattle-based carrier plans to operate 136 737s at the end of 2014 and 139 737s at the end of 2015, according to an investor update on 27 May. This is up by two aircraft in 2014 and four aircraft in 2015 from its previous update in April.

The additional aircraft will allow for an 11% increase in departures to 280 flights from Seattle Tacoma in March 2015. The move is in response to increasing competitive challenges from codeshare partner Delta Air Lines at the airport.

Alaska has leases expiring on two 737-400s through the end of 2014 and on five 737-400s and one 737-800 in 2015, Flightglobal’s Ascend Online database shows.

GECAS is the lessor of five 737-400s, including two expiring in 2014 and three in 2015, ILFC of two 737-400s expiring in 2015 and Aircastle of the 737-800 expiring in 2015, according to Ascend.

Alaska has not decided what leases will be extended but plans to work with all of the lessors in order to extend the leases that "make the most sense", it says.